Document the PMC pinctrl bindings for pad power state and signaling voltage configuration. Both nvidia,tegra186-pmc.txt and nvidia,tegra20-pmc.txt are modified as they both cover SoC generations for which these bindings apply. Add a header defining Tegra PMC pad voltage configurations. Signed-off-by: Aapo Vienamo <avienamo@nvidia.com> Acked-by: Jon Hunter <jonathanh@nvidia.com> Reviewed-by: Rob Herring <robh@kernel.org> Signed-off-by: Thierry Reding <treding@nvidia.com>